Jatropha curcas attracts attention as biological resources for production of biodiesel fuel because a non-edible Jatropha oil can be produced therefrom. Further, Jatropha is known as a plant that can be cultivated even at locations unsuited for growth of other crops in terms of water and inorganic nutrients, and is believed to be very beneficial for effective utilization of semi-arid regions and for greening. On the other hand, although Jatropha plants grow in barrens, production efficiency of oils by natural cultivating is not high because fruition of the plants is once a year and the size of the fruit is significantly smaller than that of palm. For this reason, development of highly productive Jatropha is demanded.
As one measure for improving the production efficiency of a Jatropha oil, a method of transforming Jatropha so that acetyl CoA carboxylase (ACCase) can be overexpressed for increasing the oil content of the seed is known, for example, as disclosed in Japanese National Patent Publication No. 2009-536029 (PTL 1).
On the other hand, from the view point of improving the productivity of Jatropha itself, it is also conceivable to impart drought tolerance that ensures high viability even under water deficient conditions.
Generally, growth of a plant is greatly influenced by environmental factors such as dryness, salt and low temperature, and hence development of agricultural crops imparted with environmental stress resistance is expected.
As a dry stress resistant gene recombinant plant, the one wherein the stress responsive signaling intensity and mechanism are modified so as to be adaptive or responsive to dry stress, a method for improvement to achieve overproduction of a protein molecule involved in resistance (a protein responding to environmental stresses) and the like are conceivable.
Signaling pathways responsive to environmental stresses of plants are generally classified into pathways mediated by abscisic acid (ABA) which is a plant hormone, and pathways not mediated by ABA, and further sub-classified by the type of involved transcriptional regulators. Also as to proteins involved in response, regulatory proteins involved in response such as a transcription regulator, protease and protein kinase, and functional proteins responsible for resistance such as chaperone are known, and they are believed to take part in various physiological responses (Kazuo Shinozaki et al., Asakura Plant Physiology Course 5, “Environmental response”, pp. 106-1145).
Abscisic acid (ABA) is a plant hormone that is involved in seed dormancy, opening/closing of stoma and osmotic stress resistance, and ABA is known to be deeply involved in expression of a group of stress responsive genes.
For example, NPL 1 (Wen-Xue Li et al., “The Arabidopsis NFYA5 Transcription Factor Is Regulated Transcriptionally and Posttranscriptionally to Promote Drought Resistance,” The Plant Cell, Vol. 20: 2238-2251 (2008)) reports, in a mechanism of controlling dry stress resistance in Arabidopsis thaliana, that a NF-YA5 transcription factor is ABA-dependent and is strongly induced by dry stress, and that transformed Arabidopsis thaliana overexpressing NF-YA5 is superior to wild-type Arabidopsis thaliana in resistance to dry stress.
As a method of preparing environmental stress resistant Arabidopsis thaliana, Japanese Patent Laying-Open No. 2005-253395 (PTL 2) proposes a method of utilizing an activating function of a group of genes under the control of a transcription factor that activates transcription by binding with a cis element existing upstream the gene encoding a stress responsive protein expressed due to an environmental stress (a stress responsive transcription factor). Concretely, a SRK2C gene is disclosed as a novel gene encoding a signaling factor that induces expression of DREB/CBF which is a stress responsive transcription factor, and also it is disclosed that Arabidopsis thaliana transformed to overexpress the SRK2C gene shows dominantly high survival rate in comparison with a control even after stopping of water supply.
Further, NPL 2 (Donald E. Nelson et al., “Plant nuclear factor Y(NF-Y)B subunits confer drought tolerance and lead to improved corn yields on water-limited acres”, PNAS, vol. 104, No. 42, 16450-16455 (2007)) reports that a corn NF-YB factor was identified, and a corn transformed by using this showed higher productivity under the condition of water shortage in comparison with the wild type.
Furthermore, in Japanese National Patent Publication No. 2009-540830 (PTL 3), as water deficient stress resistant plants of rice, corn, soybean and cotton, plants into which a transcription unit containing a promoter operably linked with DNA encoding a NF-YB protein of Arabidopsis thaliana, corn or soybean is introduced are disclosed. It is reported that by devising a promoter or the like, yield of the transformed plant modified to be able to overexpress NF-YB is improved in comparison with that of a wild-type control even under water deficient conditions.